Conventionally, CCD image sensors are visually checked for color reproduction errors; but it is proposed in Japanese Patent Application Laid-Open Nos. 97074/91, 100768/91 and 100769/91 to estimate reproduction errors on the basis of a quantified numerical value obtained by fusing the errors detected through statistical processing thereof, and these proposed schemes are disclosed in U.S. Pat. No. 5,204,948 issued to the inventor of this application. Moreover, the inventor proposes, in his paper "Color Reproduction Test For CCD Image Sensors," Proc. 1990 International Test Conference, pp 493-497, Washington, D.C., Sep. 10-14, 1990 (Literature 1), to test CCD image sensors by numerical values obtained by fusing and quantifying various variations detected through statistical processing.
However, these conventional schemes utilize statistical techniques, and hence they rely largely on probabilistic factors; it is impossible to definitely say, "Here is a vertical stripe," or "Here is a slanted stripe." The prior art methods are unsatisfactory in this respect.
In an example of conventional pattern recognition, each pattern contained in an image is attached a name by list processing and, to detect its shape, the pattern is matched with a template pattern prestored in a memory; the pattern recognition depends on the extent of their matching.
A neural network has also been under study as another pattern recognizing scheme.
In another example of the conventional pattern recognition techniques, image processing operators such as Laplacian, Sobel and differentiation are used to detect segments and contours. An example of such an image processing operator is shown in FIG. 1. The figure is composed of 3.times.3=9 squares, each of which corresponds to one pixel of an image to be processed. The numerical value in each square is its weighted value. The square at the center of the figure is made to correspond to the pixel being noted, then a weighted mean between it and the surrounding pixels (the sum total of products of weighted values of the nine squares and the gradation values of the corresponding pixels) is obtained, and the thus obtained weighted mean is used as the value of the center square after oerator processing. By performing this operator processing for all pixels of the image, pixels corresponding to segments and contours have large values; hence, the segments and contours are detected clearly.
The conventional pattern recognition calls for checking all templates. This inevitably involves an enormous amount of processing and consumes much time. The prior art poses problems such as the permissible limit of mismatching between the template and the actual pattern, in addition to the above-noted problems.
The pattern recognition scheme that utilizes a neural network requires a learning time and poses another problem such as the extent to which teaching patterns are regarded as identical with each other; therefore, this technique has not been put to practice yet.
The pattern recognition scheme using the image processing operator is readily affected by noise caused by dust or stains on the image and does not necessarily allows ease in detecting a continuous segment or contour. Of course, there has not been ever proposed pattern recognition equipment capable of detecting the motion of a detected segment or contour.
A first object of the present invention is to provide a spatio-temporal pulse firing basic cell which permits accurate, high-speed pattern recognition without involving matching against a template pattern and without using an image processing operator.
A second object of the present invention is to provide pattern recognition equipment which uses the above-mentioned spatio-temporal pulse firing basic cell, withstands noise and permits easy detection of a segment or contour.
A third object of the present invention is to provide pattern recognition equipment which uses the above-mentioned spatio-temporal pulse firing basic cell and permits the detection of the motion of a segment or contour.
A fourth object of the present invention is to provide pattern recognition equipment which uses the above-mentioned spatio-temporal pulse firing basic cell and permits the detection of a line component of a pattern in the direction of its travel.
A fifth object of the present invention is to provide pattern recognition equipment which uses the above-mentioned spatio-temporal pulse firing basic cell, neither involves matching against a template pattern nor uses an image processing operator but permits accurate, high-speed pattern recognition and allows a quantitative estimation of a reproduction error in an image.